Hiram d



H. D. CURRER ET AL Nov. 9 ,1926.

- TELEPHONE SYSTEM 4 Sheets-Sheet 1 Original Filed April 29, 1921 N 2511527 0P5." JfiWamDZurrzPr JZSEQEE Ea 2027 E 2 TELEPHONE SYSTEM Original Filed April 29, 1921 4 Sheets-Sheet 2 =1 606,020- H. D. @umaam ET AL TELEPHONE SYSTEM Original Filed. April 2 9, 1921 4 Sheets-Sheet 5 2771/52? 5.? Tz-zmZZZTurrier EBB an Nam 9 1926. 1,605,020

H. D. @UWQEER ET AL TELEPHONE} SYSTEEI Original Filed pril 29, 1921 4 Sheets-Sheet 4 H E-"51,5755 22m?!" li atented Nov. 9, 1926.

hearse stares entrant caries;

HIE-AM n. cnnninn, on cnlcaeo, AND enonen R- EATON, or oAKr eK, rumors, ASSXGNORS TO Kn Loee swrrcnsonnn AND snrrLY COMPANY, or onrcAeo; LLnvoIs, A conronarron or iLLInors.

TELEPHONE sYs'rEM.

Application filed rpm 29, 1921, SerialNo. 465,392. Renewed March 21 1925.

(Eur invention relates to multi-oihce telephone s; items, that is, systems in Which two or more eitonanges are interconnected by means of trunk linesa'nd in which trunking calls between exchanges are handled over these Wiresby operators in the originating exchange who pass the calls to operatorsin the distant exchanges, ivhich latter COHF plejte the connections to the called subscribers lines;

In systems-of the trunking type Which are in presentuse, A; operators are provided who; bv means of order Wires, commrmicate \i'ith- B operators at the distant exchanges, -;---i1.-;1 to them the numbers of the Wanted lines, and the B operators then in turn designte to the A operators the trunks to be u? The A operator will then insert l ng ia the cal plug ota pair into the designated trunl': ck, While the B operator plugs into the ca d line, In the system embodying our in cation We provide the A operator with a pluralitlx r local cords and in addition we cquip herposition with a number of out-goi' and incoming trunk jacks and pl tor estalglishing trunk connections. A operator reaches the B operator atthe distant exchange by inserting the calling,

eatnre or our invention is this, that when a trunking call has been completed from a calling subscriber in one exchange to th line of a called subscr'her in a distant the interoilice trunk is released upon we conclusion of conversation and as soon as e calling subscriber replaces his ediately rendered available for use as" the one above outlinedi-wi'll' be more" fully hereinafter described in the following description.

A clearer understanding of our invention may be had by referring to the accompanying drawings, in which Fig. I, Which comprises parts -2 and 3, illustrates diagram matically the apparatus used in establishing an inter-office call between-a calling and calleclsii bscriber, andflin which Fig. 2 illustrates a modification.

Fig. 3; illustrates a trunk jack having a high resistance relay connected thereto; the remainder otthe apparatiis used in conned tionwith this figure" but not shown is thesame a t that shown in Fig. 1, part2;

Per-Earring new to Fig. 1 part lflv'e have" illuuiated a .ibscribers substation A connecting the-(exchange with a hne circuit L comprising the usual line relay LR, cut-off relay GO, multiple jacks J and multiple line lamps LL, 'lhe cord circuit G, which may be used for establishing either local or trunking connections, comprises ansvverin'g phi-g" AP and a calling plug GP, the two plugs being connected by the heavily marked talking conductors. The cord circuit C comprises the usual answering and calling supervisory relays, answering and callingsupervisory signals and the necessary relay apparatus for providing the various teaturesnecess y mar-eaelephant switchboard;such as automatic 1. bring, automatic listening, secret sent ice; automatic disconnect, line lamp recalihetc. A i

The api iaraths for transferring trunking calls from one eiichange to another includes a iilhrality: of trunk i'acks TJ at each o e ators position; which terminates in multiple contacts locatedin banksot' a plurality inya' moderninanually op of finder switches as F S located at the exchange at which the call originates, and one of these switches will automatically select thejack TJ in which an operator has inserted a calling plug OP ot a cord circuit as C. The insertion of a plug CP into a trunk jack TJ .starts the travel of a switch as FS, and when the switch has completed its operation or" selecting the ack TJ into which a plug OP has been inserted, means are actuated to start the travel or a finder switch FS at the distant exchange to select a trunk circuit E as illustrated in Fig. 1, part 3.

The trunk circuit E at its incoming end terminates in a repeating coil RC, and at its 1 describe more in detail the operation of the circuit illustrated in Fig. 1, parts 1, 2 and 3. and Fig. 2.

Assuming now that a subscriber A at the xchange l3 desires to converse with a subscriber at the substation F in the exchange M, the subscriber at A initiating the call removes his receiver from its switchhook to close the switchhook contacts, which establishes an energizing circuit for the line re lay LR of the line circuit L. Line relay LR upon energization closes its alternate contact, thus establishing a circuit for the multiple line lamps LL, which lamps are distributed at the various positions in the switchboard. An operator seeing a lamp LL at her position displayed, will insert the answering plug AP into the jack J of the calling line to close an energizing circuit for the sleeve relay SL from battery through the windings of the relay SL, normal contact 2 of the line relay LD, sleeve contacts of the connected plug AP and jack J and through the winding of the cut-off relay C of line circuit L, to ground. The cut-oil relay CO is energized over this circuit and opens the energizing circuit ofthe line relay LR to eil'ace the multiple line lamps LL. The relay SL upon energization closes its alternate contact 3. and shunts out its high resistance upper winding so that if another operator has plugged into another jack of the line A, the sleeve relay SL of the second cord that has been plugged into a jack of the calling line will fail to energize because of the shunt established by the low resistance lower winding of the first sleeve relay SL, and the second operator not receiving a response when she asks for the numberwill withdraw her plug.

' The relay SL of the first cord upon energization closes its alternate contact 4:, establishing an energizing circuit for the listening relay LS, by current flowing from battery through the winding of the relay LS, alternate contact 1 of the relay SL, to ground at normal contact 5 of the sleeve relay SL. Relay LS upon energization closes its alternate contacts 6 and 7 to connect the operators set 0 to the calling line, and she now inquires the want of the calling subscriber at the substation A and learns that the subscriber F at the distant exchange is wanted. The closing of alternate contact 8 ol? the relay SL places the supervisory. relay SR across the tip and sleeve conductors of the cord circuit C. The circuit of said relay SR being traced from battery through the lower winding of the relay SR, normal contact 9 of the relay LD, ring contacts of the connected plug AP and jack J, through the closed switchhook contacts at the substation A, back through the tip contacts of the connected plug AP and jack J, normal contact 10 of relay LD, alternate contact 8 of relay SL, through the upper winding of the relay SE, to ground. The relay SR upon energization opens its normal contact 14, preventing the display of the supervisory signal SS at this time. The closing of alternate contact of relay SR establishes an energizing circuit for the meter relay MR, from battery through the winding of the meter relay MR, alternate contact 15 of the relay SE- to ground at normal contact 16 of the relay 17. The closing of alternate contact 18 of relay MR closes an energizing circuit for the meter magnet MM from battery through the winding of the meter magnet MM to ground at alternate contact 18 of relay MR, which magnet MM upon energization actuates the counter mechanism to register a call as answered by the operator associated with the cord circuit C. The operator of the cord circuit C at the exchange B, learning that the line of the wanted subscriber terminates at the exchange M, will now insert the calling plug GP into the trunk jack TJ (such trunk jack TJ being assigned for calls to be extended to the. exchange M) to start the operation of the tinder switch FS to select the trunk jack TJ, as will no be described. The operator, however. before inserting the plug CP, actuates her cut-out key OK to close its alternate contacts 19 and 20. The insertion of the plug GP into the trunk jack TJ establishes an energizing circuit for the sleeve relay SL, the relay 17 and the relay 21, the circuit of relay 17 being traced from battery through the winding of the relay 17, conductor 22, normal contact 23 of the relay LD. c nductor 24, through the wind ing of the relay 21, conductor 25, through the sleeve contacts of the connected plug GP and trunk jack TJ, to ground through ltlU liil

reoenao the winding of the trunk relay TE The sleeve relay SL has its energizing circuit closed from battery through the winding of the said relay SL", conductors 26 and 2a, through the winding of the relay 21, con ductor to groundthrough the relay TR, as above described! The energizing circuits of relays li' and SL are in" parallel and said relays SL, 17 and 21 are energized over the circuits just described due to the low resistance of the trunk relay TR. The relay 8L upon energiz ation opens its al tcrnate contact 5, opening the energizing circuit of listening relay LS, and the opening of alternate contacts 6 and T disconnects the operators set from the cord conductors. The opening of alternate contact 259 releases the busy relay BU common to her position, as will be more fully hereinafter described. Relay TR also energizes over the circuit just traced and upon energization closes its'alternate contact 28, establishing an energizing circuit traced from ground through alternate contact 28, normal contact 29 otthe relay 30, the common starting conductor SN, normal contact 30 of the switching relay SH, normal contact 31 of the or'f-noi'n'ial contacts ON, normal contact 32 of the rotary magnet RM, through the winding of the magnet RM to battery and ground. The rotary magnet RM will energize and de-energize, stepping the wipers 33, 34:, 35 and 36a first step 'from nornial into engagement with the'first set of contacts 37, 88, 89 and 40 in search of termi nails of the trunk jack Tel in which the plug Cl has been inserted. On the first step of the wipers off normal, the oil-norinal contacts ()N are shifted to their alternate positions, and successive actuations of the motor magnet RM are produced over a circuit traced from battery through the winding of the motor magnet RM, its contact 39, mal contacts ON, normal contact 41 of the switching relay SH to ground at normal contact {l2 of the bridging relay BG. Such actuations will continue each energization and de-energization of the motorlnagnet RM, stepping the wipers 33,34;,35 and36 into engagement with successive contacts 37, SS, 39 and 40 until they engage multiple contacts in their banks connected to the trunk jack TJ into which the calling plug Ci? has been placed. As soon as thewiper e aces the contact 37 associated with the trunk jack T5,.an energizing circuit is established for the bridging relay BG, traced tron: battery through the associated resisce, through the upper winding of there- "LG, normal contact 43 ,of tlie relay BG,

45 of the relay 'l-R f alternate contact 31 of the ollf-nor al contact is of relay SH, wiper 33,

The relay BG upon energization opens its normal contact 42,

preventing further energizations of the iotary magnet (saidmagnet havingal ready been shunted out by the upper w ndmg of 5G), and the closing of its alternate contact 46 establishes an energizing circuit 1: p ,I

io the relay 80 traced liom batter-y, through the upper winding oi the relay 36;, its alternate contact 46, through the lower winding of the relay 13G, wiper 34, contact erates, which relay will energize due to the L closure of alternate contact i? of relay 13G, it closes its alternate contact 30 to extend the starting wire SVV to the starting wire SW, which extends to another finder switch in the usual manner, which latter finder switch will be actuated in a similar manner, above described when a plug is inserted into a trunk jack TJ; The relay SH hay locking circuit for itself traced from hattery through the winding of the relay SH,

its alternate contact 41:8, to ground at alter irate contact 49 of the oil-normal contacts ON. The opening of normal contact ll of relay SH and the opening of normal contact 4:2 01" relay 13G open t-he circuit oi the motor magnet RM and prevent further actuation off the same. The relay BG upon energization also closes its alternate contacts 50 and 51, establishing an energizing circuit for the relay 52 of the finder switch FS at the distant exchange, said relay 52 having its windings connected across trunl; conductors 53 and 5 1, and current now flows from battery throughthe upper winding of relay 52, normal "contact 55 of the relay 56, trunk conductor 53, alternate contact 50 of relay BG, wiper 35, contact 39, the tip contacts of the connected trunk jack TJ and plug Cl alternate contact 19 of the key OK, and through the left-hand winding of the relay 5? to ground, while another circuit is established froinground through the lower winding of the relay 52, or-m1 contact 58 ot therelay 5 6, alternate contact 51, wiper 36, contact l0, ring contacts of the connected jack TJ and plug GP, alternate contact 20 'ot the key OK, throughthe righthand winding of relay 57 to battery and ground; it being remembered that at the time the operator at the exchange B insorted the plug Cl into the trunkjacl: TJ she actuated the cut-out key OK. Relays and 57 are both energized over the circuits just described, audit is to be underlng energized as above described 'closes a stood that the relay 57 is common to all cords in an operators position.

When the operator first actuated the cutout key OK, the closure of alternate contact 258 of the key OK established an energizing circuit for the relay 59, traced from battery through the winding of the relay 59,,to ground at alternate contact 258 of the key OK. The closure of alternate con tact 60 of the relay 59 connects the special tone ST through to the operators set, Via normal contact 61 of the relay 57, over conductor 62, through the tertiary winding 63 of the operators set O to ground, and the operator thus has an audible indication which continues while the finder switch FS located at the exchange 13 is functioning in seeking an idle operator at the distant exchange M, and upon the energization of the relay 52 at the distant exchange the relay 57 upon energization over the circuit just described opens its normal contact 61, interrupting the special tone ST. This interruption to the signal indicates to her that the finder switch FS has properly performed its function and has extended the call over the trunk conductors 53 and 54: to the distant exchange M, and that the finder switch FS at the distant exchange has started its travel.

The relay 52 upon energization closes its alternate contact 65, establishing an energizing circuit for the rotary magnet RM, traced from battery through the winding of the rotary magnet RM, normal contact 66 of relay 67, normal contact 68 of off-normal contacts ON, to ground at alternate contact of the relay 52, and upon energization the rotary magnet RM, through suitable pawl and ratchet mechanism, steps the wipers 69, 70 and 71 into engagement with the first set of contacts 7 2, 73 and 7 4 leading to a trunk circuit such as shown at E at the exchange M. Upon the first step of the wipers olinorinal contacts ON are shifted to their alternate positions, andit the contact 72 now engaged by the wiper 69 is a busy contact, it will be grounded, and the manner of such grounding will now be explained.

In case the first contact 72 connected by the wipers 69 is a grounded contact, circuit will be established "from battery through the winding of the relay 67 alternate contact 75 of the rotary magnet RM, normal contact 76 of the relay 77 normal contact 78 of relay 56, through the winding of relay 79 to the ground at contact 72 engaged by wiper 69. Relays 67 and 79 energize over this circuit, the relay 79 being slow to release for purposes as will be presently described. The opening of normal contact 66 of the relay 67 opens the energizing circuit of the rotary magnet RM, and the rotary magnet RM deenergizing opens its alternate contact 75, and the opening of the sa1d contact 75 opens the energizing circuit of the relay 67, and the closing of the normal contact 66 of the relay 67 due to its de-energization, will immediately re-establish an energizing circuit for the rotary magnet RM, which is again energized by current through the now closed contact 66, alternate contact 68 of the olinormal contacts ON, normal contact 76, normal contact 78, through the winding of the relay 79, to ground at the engaged contact 7 2, whereupon the rotary magnet RM steps the wipers another step, and by the closure of its contact 75 will again energize the relay 67 over the previously described circuit to the wipers 69 and to the next engaged contact, if it is busy. Thus, a seesaw action between relay 67 and motor magnet RM is produced, the slow relay 79 being in the circuit over which either one or the other is energized, and this seesaw action will continue until the wiper 69 engages a contact in its bank which leads to a trunk line in the exchange M which terminates before an operator who is not busy-that is, who is not busy establishing other trunk or local connections. WVhen the wiper 69 engages an idle, i. e., ungrounded, contact 72, no energizing circuit is established through the slow release relay 79, and the relay 79 upon deenergization closes its normal contact 80, establishing an energizing circuit for the relay 56, traced from battery through the winding of the relay 56, normal contact 81 of relay 77, normal contact of relay 79, to ground at alternate contact 82 of cit-normal contacts ON. The relay 56 upon energization closes its alternate contact 83 to establish an energizing circuit for the relay 77 traced from battery through the winding of the relay 77, alternate contact 83 of the relay 56, to ground at alternate contact 82 of the offnormal contacts ON; and the relay 77 upon energizing immediately establishes a lock ing circuit for itself traced from battery through the winding of the circuit 7 7, its alternate contact 84 to ground at alternate contact 82 of the off-normal contacts ON.

The relay 77 upon energizing opens its normal contact 81, opening the initial energizing circuit for relay 56, but a substitute circuit will be established for it, as will presently be described. The relay 56 upon the closure of its alternate contacts 55 and 58 closes an energizing circuit for the relay 85 of the trunk circuit E at the exchange M, traced from battery through the right-hand winding of the relay 57 at the exchange 13, alternate contact 20 of the key OK, ring contacts of the connected plug OP and trunk jack TJ, contact 40, wiper 36, alternate contact 51, the trunk conductor 54, alternate contact 58, wiper 71, engaged contact 7 4E, winding a of the repeating coil RC, conductor 102, normal contact 103 of relay 104:, conductors 105 and 106, through the lower winding of the relay 85, conductor306, through inding bolt the repeating coil RQ, contact 73, Wiper alternate contact 55, trunk conductor 53,31-

ternate contact 50, wiper 35, ei'igaged contact 39, the tip contacts of the trunk and plug GP, alternate contact 19,, through the leithand inding of the relay 57 to ground. The relay oftrunk circuit is energized overthis circuit, and the closure of alternatecontact 8601 the relay 85 closes an energizing circuittor the relay 8? {from batterythroughthe vinding 01" the relay 87, to grounded alternate,contact 86 of relay 85, and the closure oi alternate contact 88 ot' relay 87 extends ground to the Contact 72 engaged by the iper 69, busying said contact 72, this H ground also k extending through the winding of relay 79 through alternate contact 78 ofthe relay 56, through the Winding of the said relay to battery and ground. V e H The circuitjust traced isa substitute energizing circuit which isnow established for therelay 56, the relay 56 having been momentarily held energized, due to its slow-torelease construction. A V I I,

The relay 77 upon energization opened its normal contact 76 to prevent any further operations, of the rotary magnet RM ,until the relay 77 is again de-energized, Which can only happen after the switch ES is restored to normal and the contacts ON are shifted to their normalposition'.

The relay 87 of the trunk E at the exchange M u'ponenergizing as previously described, closes its alternate contact 89, estab lishing an 'energizing circuit for the relay 90 from battery through the winding of relay 90, to ground at alternate contact89. The closure of alternate contact 89 also establish-es an energizing circuit for the busying relay BU, traced troinbattery through the Winding of the said relay BU, normal contact 91 of the sleeve relay SL to ground at alternate contact 89 of the relay 87. The closure oi. alternate contacts 116', 117 and 118 of the busy relay BU places aground on the conductors 119,120 and 121 which lead to other trunks which terminate at the position, placing a busy potential upon the test contacts 72' or the trunk switches to which the trunks are' multipled, preventing said trunks" from being selected during the time that the operator is extendingthe con'nec ti'on to the called subscriber at the substation F. We also show a busy relay BU,

. contact 259' of the listening relay LS of the cord. that is used in establislfiin a local m 1 its alternate con .nection, to. batteryand ground through the of relay, BUT, The closure of alternatecontacts 260, 261,262 and263 connects g o to the trunk circuits terminatingat ripeness; position, the ground extendto thetest contacts'ZZ or the switches to 'vyliir zh the: "trunks niultipled, preventing said switches from seizing any trunk terminating .at herpesiuba While she isestablishing alocalconnection. '.T he closure of alternate contacts 92 and 930i the relay BU streets are operators relay OR to are trunk conductors, andthe said energizes by current through both windings ofthe relay 5? at the exchange Boyer a path which is, obvious from the"p 'revio us des'bripti'rm. T l 'u lar .O @91 energizing do e i alternate. contacts 94' endear-e connect the operators seat) of the trunk circuit rc w ht bpe a qrsse iQ lt'flle change B through alternate contacts; 96, 97

trait relay 59, an thep e acer a asexchange B being novv connected to the o deratoratthe eirchange infer; s theopGjratOr c the trunk plug T]? of the trunk circuit E into the jack J/ of the Wanted unethe o berator having, of course, fijrst tested the called line as to its idle or busy condition. y

, ,Iheclbsureof alternate contact/98 of the relay 87 establishes an energizing circuit for theindicating signal lamp IN, tracedrrom' battery through the lamp IN, normal contact 99 of the busy gua d relay GU," to ground at alternate contact 98. of therelay 87. The lamp IN lightinginforms the operator associated Witha trunk E that a call has been extended to her position a d i ch catesto her which of her trunk circuits is to be used in establishing "the connection.

After the op erator at the eXchange B has repeated the numberv of thegalled subscriber to the operator at the exchange she erestores the cutout key OK, to its normal pest tion, and the opening of alterna ,e contact 258 of the key OK ope'iiis the circuit of the relay 59, whichrelay upo restoration opens tacts 96 and97 to disconnect theoperators set 0.

The, losure of the make-beforebreak contacts 19 and 20 of the key OK establishes an energizing circuit for the supervisory relay SR of the cord circuit C at theezichange B, traced from battery through thelower "wvindin g oi the relay SR, alternate, contact lQO of the relay 17 norrnal co'ntact 101 of the ringing interrupter relay 1 RI, ,1 normal contact 20 ot the key OK ri'iigcont-acts] 0t theconnected plugCP and trunk jack TJ,

and over the trunk conductor; through the d n a t e ep ati IQ ABC .w destinies, amrn' alienataet103 at the why 1, conductors 105 and 106, through the lower winding of the relay 85, conductor 306, through the Winding b of the repeating coil RC, returning over the trunk conductor through the tip contacts of the connected plug GP and trunk jack TJ, normal contact 19 of the key OK, normal contact 107 exchange B. By dark keyshel't is meant that there is no signal displayed in connection with the operators cord after she has once completed the manual operations such "iii as inserting the plugs and operating the keys, etc., necessary in doing work in putting up a connection.

Having assumed that the line of the subscriber F is idle and that the operator inserts the trunk plug TP into the jack J of the called line, this insertion establishes a series energizing circuit for the sleeve relay SL and cut-oft relay C0 of the called line circuit L, traced, from battery through the winding of the relay SL sleeve contacts of the connected plug TP and jack J to ground through the cut-oil relay C0 The sleeve relay SL upon energizationrcloses its alternate contact 112, establishing an energizing circuit for the busy guard relay GU, traced from battery through the upper winding of the relay GU, its normal contact 113, alternate contact 114 of the relay 87, to ground at alternate contact 112 of the relay SL A locking circuit is closed through the lower winding of the relay GU traced from battery through the winding of relay GU, alter- V nate contact 99, to ground at alternate contact 98 of the relay 87'. The opening 01 normal contact 99 effaces the indicating signal IN. A locking circuit is also established through the upper winding of the relay GU traced from battery through its alternate contact 115, to ground at alternate contact 112 of the relay SL These two locking circuits of the relay GU asjust traced are for purposes as will be presently"described.

The opening of normal contact 91 of the sleeve relay SL opens the energizing circuit of the busy relay BU, which relay opensits alternate contacts 116, 117 and 118 toremove ground'from the conductors 119, 120 and 121, which conductors lead to the multiple test contacts 72 of the trunk switches FS, rendering the remaining trunks at her position selectable, as the operator has extended 4. 0 11 01 011 to the Called subscriber and is now free to receive other trunk connections, providing she is not now engaged in establishing local connections, and it she is thus occupied the trunks are rendered busy in the manner as previously described.

The closure of alternate contact 122 of the relay GU establishes an energizing circuit for the meter magnet MR, traced "from battery through the winding of the meter magnet MR, normal contact 123 of the meter cut-oil relay MO, to ground at alternate contact 122, and the meter magnet MB is now actuated to register a connection. The closing of alternate contact 122 also establishes a circuit from the meter cut-oil rea lay MO, traced from battery through the winding of the relay M0 to ground at alternate contact 122, and the meter cut-oil relay MO energizing opens its normal contact 123, preventing further actuations ot the meter magnet MR, which meter magnet MR now restores to normal.

A circuit for the ringing lamp BL is also established, traced from battery through the lamp BL, normal contact 124 of the ringing control relay RC, normal contact 125 of the ringing trip relay RT, normal contact 126 of the relay 10 1, to ground at alternate contact 112 of the relay SL The ringing lamp BL is lighted over this circuit and gives the operator of the trunk circuit E a visual indication that the called subscriber at the substation F has not as yet been signaled. Tosignal the called-tor subscriber at the substation F, the operator associated with the trunk circuit E now depresses the proper ringing key plunger of the ringing key RK to connect the ringing generator or the proper frequency to operate the call'signal ot the called subscriber at the substation F. The depression of the ringing key plunger of the ringing key RI associated with the selected frequency also brings about the actuation of the'end spring contact 127 of the ringing keyiRK, causing it to inomentarily assume its alternate positiom'and the closure of the said alternate contact 12? establishes an energizing circuit for the ringing control relay RC, traced from battery through the winding of the said relay RC, momentarily closed end spring contact 127, normal contact 126 Oil the relay 10 1 to ground at alternate contact 112 of the sleere relay SL The closing of alternate contact 28 otre lay RC establishes a locking circuit for itself, traced from battery through the winding of said relay RC, through alternate'contact 128, normal contact 125 of the ringing trip relay RT, contact 126 of relay 104., to ground at alternate contact 112 of the sleeve relay SL Relay RC upon energizing opens its normal contact 12 i. eitacing the ringing signal lamp FL. The closing of alternate contact 130 of relay RC estabthroitgh alternate Contact 136' of the ring ehetgizetiori of tl2e ifhte1 v the the subscriber at the substat thitt is; Wheh the ringing men-peel? from the selected generator frequenc is thus connected and disconnected to intermittently ope lie the call sig'hal of the called-for Suh- The rihg'ihg cement may be traced from the iihgronriclecl Pole 61 the selected generz'itor, through the clesecl cey plunger e01 tact, throhglt the winding of therihpjirig trip relay RT; alternate contact 135 or re 'lelj RI; tip eoiit-aets of theconneetecl plug TP ziri'cl jaek J, through the condenser entl cell hell of the celled. sitbstttion F. hack throhjg'h the ring Contacts of the connected nlug TP and jack J, to battery and greiintl irz'terrn vter relay RI. The cell s' T the eilhstation F is" intermittently lung tlue t6 the intermittent en'er zation and de lupter relay Bl,

1'1 F he response to his cell signal removes his receiver e1 p t from the eivitehhook. shame the sub seriher at the substation F remove his 1'-eeeiver during a ringing period, the Com- "hix'letl e enerlztor and battery flew through the wiiicling or the ringin trip relay RT ezinses the 1e to eetiizl-te; 21nd the opening cert-s normal Contact 125 opens the loelrihg ci em t or": the ringing control relay HG, ivh h relay RC restores, and the openin of its alternate contact 130" dise'enne'ets the interrupter I from the interrh'pter rehiy R1; the said relay R1 remeihing at neutral ehtihg further application l p of rihginffclfi'reh't after the Chilled subscriber at the substation F answers 111 response to his tell signal. A

Should. the strh'eeriber at the suhstetien F remove h s" reteiver (luring 51 Silent perio'rl, el'ey R1 is in one of iterle-eiierggizetl positi'ens, an e'ne'rgizir'l'gz circuit for the supervieory reht SR is established Said circuit 'beihg traced from battery through the lower idingllf ot the relay SR the wincli'rrg of the repeatihg ceil RC, normal eonltafet 136 of the relay RI, ring contacts of the cohheetetl" plug TP and jeclr J, throirgh the new cl; setl eontzrets of the sirhstetioir stfitehhook, hack th'r'mirgh the t ocontaets of the jack J and plug Tl 11L of the reley RI, alternate" Contact 137 of the sleeve relay SL3; the Winding (Z of the repeeting eoil RC, to ground thie'uglr the upper Windifigot the superviso relay The supervisory relay SR upon ehergize-- 1211 Contact 135 the non closes its alternate Contact 138, isttlvl'lli'sl'iing an energiz g circuit for the relay' 104-, traced from battery, threiigh the which mg otthe said relay elterhete' COntfiCt 138', to ground at alternate Contact 1152 of the sleeve relay Slit. The relay 104k UP'OH energ'ization closes its el'tel rate cohtnet 1 39, es tablis'h'in a locking circuit for itself traced from battery tl'lTOUg-ll the winding of the said mit 1,04, its" alternate Contact 139, to grouhtl a t alte'rhate' Contact 112 of the sleeve relay S1]. The relay 104; upon eri'ere izetion opens its h'ormal Contact 103, which opens the shunt cire'in't from z'ibout the u pper l'rig'h r'esistehce viiitling of the relay 85, but 'tlue to the feet that the sup(r-misery relay SR upon energizatio'h Closes its alternate Contact 1 10, it provides another s'httnt about the u per hi'g'h resistzh'rce \Vih'clihg of the relay 85, \Vhi'ell my he trate'tl from coed-utter 1,02, throegh elter'rlete' coh'tg'ret 1 10 of the relay SRZ-pontluetor 106'; throhgh the lower low re'sistz'thjce wifidiieg of the reltj "8'5" and o ter eolrclu'etor 306, thus allowing: the supervisory SE of the ce'rcl eiretift'c at the eX change 13 to remain energized so; theit the lmnp en emsory signal SS i'ri'tl' e cortl' eire'ljiit' C in exchange B rerirzii nsfthvrk While the subsc iber-s are talking.-

The subscriber at the" su'beta'ti on A at the exe'heinge B and the s'u hs eriloer at the substation F e; the e change M W now in con- Ve'r's'etional 'e'irenit amt the testing circuit my eeiw he wee ever the heevilg rharked 'concluc'tors. The talking eurre'rr" A suhstatlen A; Comes through the sup relay of the cord C at the exl Arl e B i W w i v aith-talking current 1S supplied to thecallecl taet 140, due to the cle-energiza;tion of the Supervisory releyfSilli removes the ehnnt from about the Upper high resistance Wineing or the relay 85, siiree relay 1041s new 111' a locked position throhgh its meme eo1itaet'139, to ground at alternate Contact the cord cireuit at the exchange B now extehftle front battery throrihh the lower Winclingot the relay-SR antl' over heavily marked trnn'k conductor} throhgh the inding (L of the rep eztting coil RC, conductor 102, through the upper high resistance Winding and lower loW resistzirice Winding of the relay 85 over conductor 306,

through the winding} 6 of the repeating eeil" RC and over the heavily marked conductor, through the upper winding of the supervisory relay SR to ground at alternate contact 110 of the relay 117. The relay SR of cord G at exchange B, due to the high re-' sistance winding of the relay 5 of the trunk circuit E at the exchange M, does not receive suiticient current to remain energized and, therefore, restores, and the closing of its normal contact 111 establishes a circuit for the supervisory signal SS, traced from battery, through the lamp SS, normal contact 145 of relay RC, normal contact 1 16 of the relay LD, normal contact 1 17 of the ringing trip relay RT, normal contact 111 of the relay SR, to ground at alternate contact 5 of the sleeve relay SL.

The subscriber at the substation A replacing his receiver upon the switchhook opens the energiging circuit of the supervisory relay SE, at the switchhook contacts. Relay SR now restores to normal, and the closing of its normal contact 1 1 establishes an energizing circuit for the link disconnect relay Ll), traced from battery through the winding of relay LD, normal contact 14, alternate contact 150 of the sleeve relay SL, to ground at alternate contact 5 of the sleeve relay SL. Relay LD upon energizing opens its normal contacts 9 and 10, disassociating the calling line from the strands of the cord circuit, and the opening of its normal contact 2 opens the circuit of the re lay SL, but the relay SL has a substitute energizing circuit established for it, traced through the alternate contact 2 of the relay LD to ground at alternate contact 5 of the sleeve relay SL. The closing of normal contact 1 1 of relay SR also establishes a circuit for the supervisory lamp SS, traced from battery through the lamp SS, normal contact 14, alternate contact 150, to ground at alternate contact 5 of the relay SL. The opening of normal contact 23 of the relay LD opens the energizing circuit of the relay 17, and the said relay 17 upon de-energization opens its alternate contacts 100 and 108, thus interrupting the cord strands of the cord circuit C from the connected trunk jack TJ. As soon asthe relay 1'? is cut off from the sleeves strands of the cord circuit C at the exchange B, due to the opening of normal contact 23 of the relay LD, there will be only one bat tery connection remaining on the sleeve strand which may be traced from battery through the winding of the sleeve relay SL', through the winding of relay 21, over conductor 25, through the sleeve contacts of the connected plug GP and trunk jack TJ, to ground through the winding of the relay TR. The relay SL is of comparatively high resistance-for instance, from 7000 to 7 500 ohms-and the current passing over the circuit just traced is .suificient to maintain the relay SL and the relay 21 energized; but the relay TR, owing to its relatively low resistance and the adjustment of its spring contacts, d-e-energizes, and its contacts 28, and 17 restore to normal. The opening of alternate contact 17 opens the energizing circuit of the relay BG, which relay tie-energizes, and in so doing its alternate contacts and 51 are opened, opening the talking conductors extending through to wipers 35 and 36.

Upon the closing of normal contact 42 of relay 13G, upon its de-energization an energizing circuit is established for the release magnet RR, which may be traced from battery through the winding of the release magnet RR, alternate contact 41 of the relay SH, to ground at normal contact 42 of the relay 13G, which is now at normal, and the release magnet RR upon energizing withdraws the retaining pawl of the switch, and the wipers 33, 34L, 85 and 36 are springre-stored to normal.

The opening of contact i7 of relay TB, of course tie-energizes the relay 30, and upon the wipers restoring to normal the oilnormal contacts ON are moved to their normal position, and all the mechanism of the finder switch F-S at the exchange 13 is now at normal.

Upon the opening of alternate contacts 50 and 51 of the relay BG, the relay 85 at the trunk circuit E at the exchange M has its circuit opened and consequently is de-energized. The opening of its contact 86 opens the energizing circuit of the relay 87, and the relay 87 upon de-energization opens its contact 89, which allows the relay 90 to deenergize. The opening of: alternate contact 88 removes ground from the contacts 72 at the exchange E, and as the relay 90 is of a slow-to-release construction, it will keep its contact 160 in its alternate position long enough to insure that the relay 56 of the switch FS will restore, and the relay 56 upon de-energization opens its alternate contacts 55 and 58, placing the wipers and 71 on open circuit. The closing of normal contact 83 of the'relay 56 closes an energizing circuit for the release magnet RR, traced from battery through the winding of the magnet RR, through alternate contact 161 of the relay 77, normal contact 83 of relay 56 to ground at the alternate contact 82 of the oft-normal contacts ON. The release magnet RR upon energization withdraws the retaining pawl of the switch, and the wipers 69, 70 and 71 are spring-restored to normal, and when the wipers 69, 70 and 71 reach their normal position, the oil-normal contacts ON are moved to their normal positions, and the opening of contact 82 opens the release magnet RR, and the mechanism of the tinder switch F S at the exchange E is at normal.

It is thus seen that when the two subscribers have finished conversation and have replaced their receivers, the two switches FS and F5 are released and fully restored so that they are immediately tree, thus rendering the trunk line promptly available for another connection.

The operator at the exchange B, noting the signal lamps SS and SS displayed, witl'uilraws the plugs AP and GP, and the withdrawal of the plug GP from the trunk jack TJ brings about the de-energization of the sleeve relay SL and the relay 21. The relay SL upon de-energization opens the circuit 01 the link disconnect relay Ll), and the relay LD upon de-energization opens its alternate contact :2 to open the energizing circuit of the sleeve relay SL. The apparatus ot the cord circuit C at the exchi nge ll is now at normal and available for use in establishing other connections.

T he relay 87 at the trunk ci-rcuitE oi' the exchange M upon de-energization closes a circuit for the disconnect signal DS, traced from battery through the lamp DS, alternate contact 165 of relay SL to ground at normal contact 98 ct therela-y 87, and the operator of the trunk circuit E at the exchange M observing the disconnect signal DS now ithdraws the trunk plug TP from the jack J of the subscribefis line, opening the series energizing circuit of the sleeve relay SL and cut-oil relay CO and the open ing of alternate contact 1120f the relay SL permits the de-energization of the relay and the relay GU. The apparatus at the trunlr circuit E is now at normal and avai able for use in establishing other connections.

The calling subscriber at the substation A of exchange l3 upon replacing his receiver upon the switchhook, immediately disconnects his line from the connected cord circuit C due to the energization of the relay LI) and thus places the line relay LR- ot the line circuit oi the calling subscriber under his control, so that it he wishes to recall he may do so by again removing his receiver, even though the plug AP remains in the jack J, and his act of removing the receiver again brings about the eueigization oil the line relay LE to light the multiple line lamps LL so that any one of a plurality of operators may seize the recall.

Assuming now that the calling subscriber is the first to replace his receiver upon the switchhook, the replacing ot' the receiver opens the energizing circuit of the supervisory relay SE at the switc'hhook contacts, and the closing of normal contact 14 establishes an energizing circuit for the link disconnect relay LD from battery through the winding of relay Ll), normal contact 14, alternate contact 150 to ground at alternate contact of the relay SL. The closing of normal contact lt also establishes an energizing circuit for the supervisory signal SS to ground at alternate contact 5 of the sleeve relay SL. The opening of normal contact 2 opens the initial energizing circuit for the sleeve relay SL, but substitute circuit for the said relay SL is established, as previously described, to ground at alternate contact 5 of the relay SL. The opening of normal contact 23 ot' the relay LD opens the energizing circuit of the relay 1?, and the relay 17 upon restoration opens its alternate contacts 100 and 108, disconnecting the cord conductors from the connected trunk jack Tl, The sleeve relay SL and the relay 2.1 are the only relays now connected to the sleeve conductor of the cord C, and due to the high resist-- ance of the sleeve relay SL, as before clescribed, the relay TB of the trunk jack TJ does not receive suliicicnt current and, there fore, restores to normal.

The relay TR- upon de-energization opens its alternate contacts 28, l5 and 47, and the opening of alternate contact 47 opensvthe energizing circuit of the relay 13G, which relay tie-energizes, and in so doing its alternate contacts 50 and 51 are opened, opening the talking conductors extending through the wipers 35. and, 36. The relay BG upon de-energization closes its normal contact 42, establishing an energizing circuit for the release magnet RR, which magnet ER withdraws the retaining pawl of the switch and permits the restoration of the wipers 33, 34, and 36 to normal, as previously described. Upon. the opening of alternate contacts and 51 of the relay BG, the relay 85 of the trunk circuit E at the exchange M has its circuit opened and consequently deenergizes. The retraction of the' alternate contact 86 of the relay 85 opens the energizing circuit of the relay 87, and the relay 87 upon de-energization opens its alternate contact 89, which allows, the relay 90 to deenergize. The opening of alternate contact 88 removes the ground from the test contacts 72 of the switch FS at the exchange M. The removal of this ground allows the relay 56 to restore, and the opening of alternate contacts and 58 places the wipers and 71 on open circuit, and the closing of normal contact 83 of the relay 56 closes an energizing circuit for the release relay RR, and the release magnet upon energizing withdraws the retaining pawl and allows the wipers to restore to normal, the ofl' normal contacts ONalso restoring.

The called subscriber at the substation F replacing his receiver opens the energizing circuit of the supervisory relay SR and the restoration of the relay 87, due to the do energization of the relay 85 closes a circuit for the disconnect signal DS as previously described, and the operator noting the lighted disconnect signal DS, withdraws the trunk plug T]? from the jack J, which withdrawal allows the sleeve relay SL to restore to normal, bringing about the effacement of the signal DS. The opening of alternate contact 112 of the relay SL opens the locking circuit of the relay 10 1. The apparatus used in establishing a connection between the calling subscriber at the substation A of the exchange I5 and the called subscriber at the substation F at the exchange M is now at normal and available for use in establishing other connections.

From the previous description it may be seen that the calling subscriber of the substation A at all times controls the disconnection of the finder switch FS at the exchange B, and the finder switch FS at the exchange M.

In case the called subscriber at the substation F at the exchange M is being signaled and does not answer the call, the calling subscriber at A in replacing his receiver upon the switchhook will de-energize the supervisory relay SE in the cord circuit C, and the relay SR de-energizing closes the circuit through the link disconnect relay LD. The relay 17 has its circuit opened at the contact 23 of the relay LD, and it is plain from the preceding description that the switch FS will restore, as does also the finder switch FS, and circuit being opened through the wipers 7 0 and 71 of the switch FS, relay 85 of the trunk circuit E of the exchange M Clo-energizes, bringing about the restoration or the relay 87. The relay 87 upon restoration opens its alternate contact 131, interrupting circuit through the ringing interrupter relay RI, thus disconnecting ringing current from the called line. Ringing control relay RC remains energized over the circuit hereinbefore traced to prevent the ringing lamp RL from burning. lhe closing of normal contact 98 of relay 87 l1ghts the disconnect signal DS, and the operator of the trunk E at the exchange M now withdraws the plug TP and the operator at the exchange B receiving disconnect signals SS and SS, withdraws the plugs AP and GP from the respective jacks J and TJ, and the apparatus used in establishing this at tempted connection is now at normal and available for use in establishing other connections. 7

Assuming now that the calling subscriber at the substation A removes his receiver to initiate a call for a subscriber in his own exchange, the operation of the-line circuit L and the cord circuit C of Fig. 1, part 1, will be the same as that already described, until after the operator has received the number of the calling subscriber. In this case she will test a multiple jack of a called subscribers line whose line circuit and substation will have exactly the same arrangement as that of the subscriber A. To make the test the operator touches the tip of the plug GP to the sleeve of the jack of the called line. If the said called line is busy because the plug of another cord circuit has already been placed into a multiple of the jack to be tested provided always a subscriber has not effected automatic disconnection), there will be a potential on the tested sleeve contact of the jack, and an impulse of current will flow through the tip of the plug GP, normal Contact 19, normal contacts 107 and 108, the closed contact 200 of the relay LS, and to ground through test relay T, which is common to an operators position. The relay T upon energization will actuate to close its alternate contact 201 to close battery through the tertiary winding 63 of the operators induction coil, giving her the customary busy click.

We also provide testing means for giving the operator a revertive tone test it she is testing a multiple jack of a line in which she has already inserted the answering plug of the cord, that is, if the calling subscriber at the substation A. wants another subscriber on his own line; the system thus providing for a case in which there are a number or substations connected to a single line. In making such a revertive test the operator will receive the click as usual, but in addition the closure of alternate contact 202 of the relay T will connect the revertive tone test ST, the special tone circuit being traced from the tone device ST, alternate contact 202 of the relay T, alternate contact 203 of the relay LS, normal contact 2 of the relay LD, through the sleeve contact of the plug AP to the sleeve of the jack J into which that plug is inserted, thence to the sleeve of the jack that is being tested and over the tip of the calling plug GP, through normal contact 19 of the key OK, normal contacts 107 and 108, through alternate contact 200 of the relay LS, to ground through the tertiary winding 63 of the operators induction coil. The operator hearing this special tone will know it is a revertive call and tell the calling subscriber to momentarily replace his receiver, and the operator will then withdraw the plug AP, inserting the calling plug GP and ring in the usual manner.

Assuming that the called-for substation is on an idle line and entirely independent of that of the subscriber at the substation A, the operator receiving no click upon her test, inserts the calling plug GP into the non-busy jack, thus placing the sleeve rel-av SL and the relay 17 of the cord circuit C in connection with the ground through the winding of the cut-oft" relay C0 of the called line. The circuit of relay 17 and the circuit of relay SL extend through the winding of the relay 21, and due to the high resistance of the cut-off relay C0 of the called line the relay 21 does not operate, but the relays Si] and 17 operate over the circuit just described. The operator associated with the cord circuit- Chow actuates one of the ringing key plungers of'the ringing key BK con nected with the ringing generator of the proper frequency to actuate the call bell at the called substation. The depression of her ringing key plunger of her rin'ging key RR momentarily closes the end spring contacts 20 1 and 205, and the closing of the ringing key ,end spring contact .205 closes an energizing circuit for the ringing control relay RC, traced from battery tl rough the winding of the relay RC, momentarily closed end spring contact 205, normal contact 1 16 of the relay LD, normal contact 1417 of the ringing trip relay RT, normal contact 111 of the supervisory relay SR" to ground at alternate contact 5 of the sleeve relay SL, and the closing of alternate contact 145 of the relay RC closes locking circuit for itself from battery through the Winding of the said relay RC, its alternate contact 1-15', through normal contact 146 of the relay LD and over the previously described path to ground at alternate contact 5 of the sleeve relay SL'. The momentary closure of the end spring contact 204: closes an energizing circuit for the ringing interrupter relay RI traced from battery, through the upper winding of the relay RI, closed end spring contact 2045 to ground at alternate contact 206 of the ringing control relay RC, so that the called substation is instantly rung and will continue to be rung as long as the op erator keeps the end springs 20% and 205 shifted, the ringing current extending from the generator through the depressed key plunger, through the lower winding of the relay RT. alternate contact 10$" of the relay 11, and through the condenser and call bell at the called substation and back to battery and ground at alternate contact 101 of the relay RI. y

When the operator releases the ringing key plunger, the end springs open their contacts 204: and 205, and as the relay RChas closed a locking circuit for itself, as described, the constantly rotating interrupter I is connected to the ringing interrupter relay RI, traced from battery through the lower winding of the relay RI, alternate contact 207' of the relay BC to ground through the constantly rotating interrupter I. The relay RI will be thus intermittently energized and de-energized to connect and disconnect ringing current through its alternate contact 107, ringing current being traced from the selected generator through the lower winding of the ringing trip relay RT, alternate contact 107 of the relay RI, normal contact 19 of the key OH, tip contacts of therconnected plug CPand jacket the called line, througli the call bell and condenser at the called substation, the ring contacts of the connected jack and plug GP, normal contact 20 of the key GK to battery and ground through alternate contact 101 of the relay RI. 7

Should the subscriber answer during a ringing period, the reduced resistance at the substation caused Ly the removal. of the receiver allows sufiicient current to flow through the lower winding 0]": the relay lt to energize it, and the said relay RT upon energization opens its normal; contact 1 17, opening the locking circuit of ringing control relay RC, and the said relay RC upon restoration opens its alternatecontact 207, interrupting the circuit for the ringing interrupter relay RI, thus preventing further energizations and d'e-energizations-of the relay RI and preventing further application of ringing current to the called line.

If the called subscriber removes his receiver during a silent period, the normal contacts 101 and 107 ofthe ringing inter rupter relay RI will be closed and the supervisory relay SR will immediately ener 'gize through the now closed contacts Of the subscribers switchhook, and the opening of normal contact 111 ofthe relay SR will open the locking circuit 01 the ringing control relay EC to prevent further energiza- 'tions and de-energizations of the ringing intcrrupter relay The calling and called subscribers are now in conversational circuit, which may be traced over the heavily marked conductors.

Assuming now that the subscribers have finished conversation and that the called subscriber is the first to replace his receiver upon the switchhook, the opening" of the switchhook contacts at the called substation opens the. energizing circuit for the supervisory relay SR, and the closing of normal contact 111 of the supervisory relay SR establishes a circuit for the supervisory signal SS from battery through the said lamp, normal] contact 145, normal contact 146 of relay LD, normal contact 147 of relay RT, normal contact 111 oi relay SR, to ground at alternate contact 5 of the sleeve relay The relay 17 does not de-energize at thistime due to the fact that the callin sub scriber has not as yet replaced his receiver upon the switchhook, and the replacing of the receiver at the called substation at this time does not disconnect said called line from the connected cord. 7

When the calling subscriber at the substation A replaces his receiver upon'the switchhook, the opening of the switchhook contacts opens the energizing circuit of the supervisory relay SR, and the closing of normal contact 14 of the relay SR closes an energizing circuit for the link disconnect relay LD from battery, through the relay LD to ground at alternate Contact 5 of the sleeve relay SL. The relay LD upon energization opens its normal contact 23, opening the energizing circuit of the relay 17, and the relay 17 de-energizing opens its alternate contacts 100 and 108, disconnecting the cord conductors from the line of the called subscriber, and the energization of the link disconnect relay LD brings about the opening of its normal contacts 9 and 10, also disconnecting the answering end of the cord circuit from the line of the calling subscriber. Upon the de-energization of the relay 17, the sleeve relay SL and the relay 21 are the only relays now connected to the sleeve strand of the cord and due to the high resistance of the sleeve relay SL' of the cord circuit C, the cut-01f relay of the line circuit of the called line does not receive sufficient current to hold it up and it restores to normal, again placing the line relay under the control of the called subscriber, so that the called subscriber may initiate a recall. Upon the energization of the link disconnect relay LD of the answering end of the cord circuit C, the sleeve strand of the cord is opened at the normal contact 2 of the relay LD. thus permitting the cut-off relay of the calling line to restore to normal and placing the line relay LR of the calling line under the control of the calling subscriber so that he may immediately recall upon the replacement of his receiver upon the switchhook. Should the calling subscriber replace his receiver upon theswitchhook first, the supervisory relay SR will restore to normal and the closing of its normal contact 14 energizes the link disconnect relay LD, and the link disconnect relay Ll) energizing disconnects the line of the calling subscriber in the cord circuit, as before described.

The opening of the normal contact 23 of the link disconnect relay LD does not aiiect the relay 17 at this time, due to the circuit through contact 240. Should the called subscriber not as yet have placed his receiver upon the switchhook, under these conditions the supervisory relay SR is still maintained energized over the called line, and the relay 17 will remain energized from battery through the winding of the relay 17, alternate contact 240 of the'relay SR, normal contact 241 of the relay 21 (relay 21 not energizing when the cord circuit C is used for establishing a local connection, due to the comparatively high resistance of the cut-off relay C0 of the line circuit of the subscriber), through the winding of the relay 21, conductor 25, sleeve contacts of the connected plug GP and the jack of the called line, to ground through the cutoff relay of the called line circuit.

Now, when the called subscriber replaces his receiver on the switchhook, the supervisory relay SR restores and the opening of its alternate contact 2 10 opens the energizing circuit of the relay 17, and the relay 17 upon restoration opens its alternate contacts 100 and 108, and the operation of the circuit from this point on is the same as previously described.

Referring now to Fig. 2, we illustrate a cord circuit C similar to that of Fig. 1, part 1, and which may be substituted in place of Fig. 1, part 1, in connection with Fig. 1, parts 2 and 3. Corresponding relays and apparatus bear the corresponding reference characters, but with an exponent added. The operation of the circuit is similar to that of Fig. 1, part 1, and the calling end of the cord C is adapted to operate in connection with a low-wound cut-0E relay of the called line when establishing a local connection, and a high resistance trunk relay when operating in connection with a trunking connection. When the calling plug GP of the cord C is inserted in a local jack of a called line due to the low-wound cut-cit relay, relays 17 and SL operate over a parallel circuit, the circuit of relay SL being traced from battery through the winding of relay SL conductors 275 and 276, the sleeve contacts of the plug GP and jack of the called line, to ground through the cut-ofi relay of the called line, and the circuit of relay 17 being traced from battery through the winding of relay 17 conductor 277, normal contact 23 of relay LD', conductor 278, through the winding of relay 21', conductor 276, to ground through the cut-off relay of the called line. All three relays, namely, SL, 21 and 17 operate over this circuit due to the low resistance of the cut-off relay. When the called subscriber answers, the supervisory relay SR operates and closes its alternate contact 279, and as contact 280 of relay 21 is closed due to its energization, relay 17 is placed under the control of the called subscriber.

hen conversation terminates, should the calling subscriber at A replace his receiver first, the link disconnect relay LD' will operate, as is obvious from the previous description, but the opening of contact 23 of relay LD does not bring about the de-energization of relay 17 at this time, as the said relay is maintained energized through alternate contacts 27 9 and 280 of relays SR and 21 and through the winding of relay 21 to ground.

Now, when the called subscriber replaces his receiver, the supervisory relay SR restores, and the opening of its alternate contact 279 opens the energizing circuit of relay 17 and the relay 17 restores and disconnects the cord conductors. Relay SL is now the only relay connected to the sleeve strand and (due to its high resistance) the cut-off relay of the called line fails to remain energized, and it restores for purposes as previously described in connection With Fig. 1, parts 1, 2 and 3. Should the called subscriber replace his receiver first, the relay SR restores, but relay 17 is maintained energized through normal contact 23 of Ll), and when the calling subscriber replaces his receiver relay LD' will energize to open the circuit of 17 and the operation of circuit from this point will be the same as already described.

When a connection is extended over a trunk to a distant exchange, relay 21 Will not operate due to the high resistance of the trunk relay TB of the trunk circuit, as shown in Fig. 3, so that the relay 17 Will be solely under the control of the calling subscriber, as the contact280 of relay 21 remains open due to its failure to operate, and as soon as thecalling party replaces his receiver relay LD will operate to open its normal contact 23, thus allowing relay .17 to restore, and the operation of the circuit from this point on is the same as previously explained.

lVhile We have illustrated and described a particular embodiment of our invention, it is to be understood that We do not intend to be limited to the particular structure which is herein described and illustrated, but intend to cover all such changes and modifications as come Within the spirit and scope of the appendedclaims. 7

Having described our invention, hat We .claimvasnew and desire to secure by United States Letters Patent, is: p i

1. In a telephone system, an operators cord circuit having a calling plug, a pair of telephone lines including a calling and a called station adapted to .be connected With said plug, apparatus solely controlled from the calling station adapted to operatively free one of said lines When it is connected to said p'lug,'andautomatic switching means eiiective to place the operatively freeing of said other telephone line under joint control of the calling station and the called station when said other line is connected With said plug. r

2. Ina telephone'system having a linkcircuit provided With a terminal for interchangeable connection With telephone lines, automatic means under the sole control of a calling subscriber to operatively free said telephone line at the end of conversation, another telephone line adapted for connection Withsaid terminal, and automatic means for operatively freeing said other line at the end of conversation, said means controlled by a called subscriber.

In a telephone system, a link circuit connected to a calling line, a terminal for said link circuit and a called line connected therewith, and relay mechanism automatically and solely controlled over the calling line to operatively tree thecalled line at the end of conversation, another line for con- ;a terminal for nection to said terminal as a called line, and relay mechanism then automatically and jointly controlledover the calling line and the called line to operatively free the called line at the end of conversation.

l. A telephone system including ,a calling line and a called line and a. plurality of switchboard operators manually operated link circuits for interconnecting said lines, automatic selecting and connecting mechanism between said link circuits and operated to (connect them, means applying current to signal the called substation, and relay devices operableover the calling line effective to discontinue said current and to tree said calling line from said link circuits and said mechanism, said called line and its associated linkcircuit remaining connected.

A telephone system including telephone lines and a link circuit for connecting them, a relay controlling the talking conductors of said circuit, solely controlled from the calling, station when said link circuit connects said station in conversational relation With one oil said lines, ,and means automati callyoperated to place said relay under con trol of a called station When said link circuit connects the calling station With an other ofsaid lines.

6. A telephone system including telephone lines and a link circuit for connecting them, a link circuit relay operated when COl'lIlGC-r .tion is made to'aline With a loW resistance connection, said relay inoperative When connection is made to a line with a high resistance connection, automatic disconnect apparatus solely controlled over one of a pair of connected lines When said link circuit relay is in onecondition, and jointly controlled over the tvvoconnected lines When said relay :is in the other condition.

7. A telephone system including subscribers lines andian operators cord circuit for connecting them, a pair of relays for the calling cord operated in parallel over a strand of said cord, and a third relay in the :common connection of said relays, said tWo relays operating hen connection is made to any line and said third relay operat- :ing when connection is made to certain lines only, automatic disconnect apparatus responsive to the establishmentof certain circuit conditions When said third relay is operated and to the establishment of certain other Icircuit conditions when said third relay is unoperated. i

,8, Atelephone system having telephone hues and :a link circuit to interconnect them, said circuit (for establishing connection directly to a called line, or to a trunk circuit adapted for connection to the called line, va marginal relay operating or remaining inert according to the character of the connections as aforesaid made by said terminal, and automatic disconnect apparatus controlled by said relay and operable by one of a pair or connected lines.

9. A telephone system including telephone lines and a link circuit for connecting them, a relay for said link circuit controlled by the calling subscriber, and a second relay therefor controlled by the called subscriber, means for connecting said link circuit directly to a called line, or to another link circuit for connection to the called line, and automatic disconnect apparatus solely controlled by one of said relays or jointly by them according to which of the connections aforesaid has been made.

10. A telephone system including telephone lines and a link circuit for connecting them, a pair of relays for said link circuit, one controlled by the calling subscriber and the other controlled by the called subscriber, a marginal relay for said link circuit, actuated when connection is made to a low resistance circuit and inert when connection is made to a high resistance circuit, and an electromagnet responsive to open a talking strand of said link circuit, controlled by one of said pair of relays or jointly by the two according to the operative condition of said marginal relay.

11. A telephone system including a calling line and called lines, a link circuit having manually operated connection terminals 'at each end thereof "for interconnecting said calling line and said called lines directly by said link circuit or said link circuit and a trunk circuit in conversational circuit, automatic means for disassociating said link circuit from the called line, controlled solely by the calling subscriber under said link circuit and said trunk circuit conditions and controlled jointly by the calling and called subscribers under said directly connected link circuit conditions. 7

12. In a telephone system including a calling line and called lines of different classes, a link circuit :for interconnecting said calling line with any one of said called lines, automatic means for freeing said calling and called lines from said link circuit although a physical connection remains between said link circuit and said calling and called lines, said automatic means controlled solely over thecalling line when connection is made with one class of called lines, and controlled jointly over the calling and called lines when connection is made with the other class of called lines.

13. A telephone system including a calling line, a called local line and a called trunk line, a link circuit having manually operated connection terminals at each end thereof for interconnecting said line and said local or trunk line in conversational circuit, electromagnetic means for said link circuit tor freelng said calling line and the called line from said link circuit, said electromagnetic means controlled solely by the calling subscriber when connection is made with said trunk line, and controlled jointly over the calling and called lines when connection is made with said local line.

1a. In a telephone system including telephone lines terminating at a local exchange, and telephone lines terminating at a distant exchange, switchboard op'er'ators manual link circuits for interconnecting said lines at the local exchange or for connecting the local telephone lines with the telephone lines at the. distant exchange, automatic disconnect means individual to said link circuit for freeing the calling and called lines from the link circuit connecting them, said means controlled solely over the calling line when said calling line is connected to a called line at the distant exchange, and controlled jointly over the calling and called lines when said calling line is connected to a line at said local exchange.

15. In a telephone system including tele phone lines some of which terminate in local jack terminals while others terminate in trunk jack terminals, link circuits for connecting said telephone lines in conversational circuit, automatic link disconnect means individual to said link circuit and controlled solely over the calling line when connection is made with a trunk jack terminal to free the calling and called telephone lines from the link circuit connecting them and controlled jointly over the calling and called lines when connection is made with a local jack terminal.

16. A telephone system including a calling telephone line and called telephone lines, link circuits for interconnecting said calling line with said called lines via said link circuit or said link circuit and a trunk circuit, and automatic means for operatively but not physically disassociating a connected link circuit from the calling and called lines, said means controlled under said link and trunk connection conditions solely over the calling line and under link connected conditions jointly over the calling and. called lines.

17. A telephone system including a calling line and called lines, a link circuit having manually operated connection terminals at its opposite ends for interconnecting said calling line and said called lines via said link circuit or said link circuit and a trunk circuit, automatic means for disassociating said link circuit from the called line controlled solely by the calling subscriber during a link and trunk connection, and controlled jointly by the calling and called subscribers during a link circuit connection.

18. A telephone system including subscribers telephone lines, a link circuit havat the opposite ends thereof for interconmeeting said lines via said link circuit or jointly by a calling and a called subscriber said link circuit and a trunk circuit, electroduring a'link circuit connection. magnetic means for said link circuit for Signed by us at Chicago, in the county 10 freeing the called line and the calling line of Cook and State of Illinois, this 26 day 5 from said link circuit, said means controlled of April, 1921.

solely by the calling subscriber during a I-IIRAM D. CURRIER. link and trunk connection, and controlled GEORGE E. EATON. 

